Direct fuel injection has been applied to gasoline engines to improve engine efficiency and performance. Further, injecting gasoline or a gasoline and alcohol mixture directly into an engine cylinder reduces transient fueling errors that may be observed on port fuel injected engines. However, direct fuel injected engines may increase particulate emissions of a gasoline engine. The particulate emissions may result from incomplete vaporization or poor mixing of the injected fuel. Incomplete vaporization is particularly likely to occur if the injected fuel impinges on a combustion surface which is not sufficiently hot to support fuel evaporation prior to combustion. This can result in fuel puddles in the combustion chamber, which produce high particulate emissions when burned. This change in fuel vaporization and puddling behavior as a function of combustion system temperature requires careful scheduling of fuel injection events to optimize engine behavior.
The inventor herein has recognized the above-mentioned disadvantages of direct fuel injected engines and have developed a method, comprising: operating a first cylinder of an engine while a second cylinder of the engine is deactivated; reactivating the second cylinder in an engine cycle where the first cylinder is supplied a first actual total number of fuel injections and injection timing; and supplying the second cylinder a second actual total number of fuel injections and injection timing different than the first actual total number of fuel injections and injection timing during the engine cycle.
By supplying a previously deactivated cylinder with a different number and timing of fuel injections than a cylinder that has been active while the cylinder was deactivated, it may be possible to reduce the fuel impingement on cold combustion surfaces of the newly reactivated cylinder and provide the technical result of reducing particulate formation in the newly reactivated cylinder while maintaining emissions and efficiency in the cylinder that remained active. For example, the number of fuel injections provided to the previously deactivated cylinder during an engine cycle may be greater than a number of fuel injections provided to the cylinder that remained active. Additionally, the timing of the fuel injection(s) provided to the newly reactivated cylinder may be later in the combustion cycle than for the cylinder that remained active. The additional fuel injections and/or later injection timing may help to reduce fuel impingement and improve fuel vaporization and mixing in the previously deactivated cylinder. One the other hand, the number of fuel injections provided to the cylinder that remained active may be fewer, and the timing of the fuel injections may be earlier, than the number and timing of fuel injections supplied to the previously deactivated cylinder so that CO emissions an fuel consumption of the cylinder that remained activated may be maintained at an optimum level for the hot combustion chamber.
The present description may provide several advantages. In particular, the approach may reduce engine particulate emissions. Additionally, the approach may improve vehicle fuel economy by allowing active cylinders to continue to operate with the most efficient fuel injection settings. Further, the approach may provide more consistent vehicle emissions after reactivating engine cylinders.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.